J/A+A/690/A222 Abell 754 MeerKAT and XMM images (Botteon+, 2024)
The prototypical major cluster merger Abell 754.
I. Calibration of MeerKAT data and radio/X-ray spectral mapping of the cluster.
Botteon A., van Weeren R.J., Eckert D., Gastaldello F., Markevitch M.,
Giacintucci S., Brunetti G., Kale R., Venturi T.
<Astron. Astrophys. 690, A222 (2024)>
=2024A&A...690A.222B 2024A&A...690A.222B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; X-ray sources ; Radio sources
Keywords: radiation mechanisms: thermal - radiation mechanisms: non-thermal -
shock waves - galaxies: clusters: general -
galaxies: clusters: intracluster medium -
galaxies: clusters: individual: A754 -
Abstract:
Abell 754 is a rich galaxy cluster at z=0.0543 and is considered the
prototype of a major cluster merger. Like many dynamically unrelaxed
systems, it hosts diffuse radio emission on Mpc-scales. Extended
synchrotron sources in the intra-cluster medium (ICM) are commonly
interpreted as evidence that a fraction of the gravitational energy
released during cluster mergers is dissipated into nonthermal
components. Here, we use new MeerKAT UHF- and L-band observations to
study nonthermal phenomena in Abell 754. These data are complemented
with archival XMM-Newton observations to investigate the resolved
spectral properties of both the radio and X-ray cluster emission. For
the first time, we employed the pipeline originally developed to
calibrate LOFAR data to MeerKAT observations. This allowed us to
perform a direction-dependent calibration and obtain highly sensitive
radio images in UHF- and L-bands which capture the extended emission
with unprecedented detail. By using a large XMM-Newton mosaic, we
produced thermodynamic maps of the ICM. Our analysis reveals that the
radio halo in the cluster center is bounded by the well-known shock in
the eastern direction. Furthermore, in the southwest periphery, we
discover an extended radio source that we classify as a radio relic
which is possibly tracing a shock driven by the squeezed gas
compressed by the merger, outflowing in perpendicular directions. The
low-luminosity of this relic appears compatible with direct
acceleration of thermal pool electrons. We interpret the observed
radio and X-ray features in the context of a major cluster merger with
a nonzero impact parameter. Abell 754 is a remarkable galaxy cluster
showcasing exceptional features associated with the ongoing merger
event. The high quality of the new MeerKAT data motivates further work
on this system.
Description:
Our observing program on A754 (Proposal ID: SCI-20220822-AB-01) made
use of MeerKAT UHF- and L-band receivers for a total time of 20 hours.
The 10 hours observation in each band was split into 5 hour-observing
runs, two "rising" tracks on 2023 January 6 and 7 (Capture Block
IDs: 1673038580 and 1673124676) and two "setting" tracks on 2023
March 25 and 26 (Capture Block IDs: 1679769376 and 1679855479), to
maximize the uv-coverage on the target. Data were recorded using 4096
channels covering the frequency ranges 544-1088MHz (UHF band) and
856-1712MHz (L band) and adopting an integration time of 8s.
A754 was observed 13 times with XMM-Newton. The four earlier
observations took place in 2001 and 2002 (ObsIDs: 0112950301,
0112950401, 0136740101, 0136740201; PI: Turner) and covered the
central region of the cluster. In 2008, two deep observations targeted
the shock region (ObsIDs: 0556200101, 0556200501; PI: Leccardi) and
one was off-set from the cluster (ObsID: 0556200301; PI: Leccardi).
The six latest observations, conducted in 2019 and 2020, covered the
cluster outskirts in various directions (ObsIDs: 0821270601,
0821270801, 0844050101, 0844050201, 0844050301, 0844050401; PI:
Ghirardini).
The radio observations were performed with MeerKAT in UHF and L band.
The X-ray observations comprise 13 ObsIDs carried out with XMM-Newton.
Objects:
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RA (2000) DE Designation(s)
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09 09 08.4 -09 39 57.996 Abell 754 = ACO 754
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 155 4 List of fits images
fits/* . 4 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.date Observation date
52- 61 F10.5 MHz Freq ? Observed frequency
63- 68 I6 Kibyte size Size of FITS file
70- 98 A29 --- FileName Name of FITS file, in subdirectory fits
100-155 A56 --- Title Title of the FITS file
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Acknowledgements:
Andrea Botteon, andrea.botteon(at)inaf.it
(End) Patricia Vannier [CDS] 26-Aug-2024